This project investigates muscle coordination during lower limb force generation. Walking disability is a major consequence of post-stroke hemiparesis. Walking is impaired by an inability to generate adequate force and to direct those forces appropriately. This proposal focuses on mechanisms of foot force control in order to develop therapies that can take advantage of these control mechanisms. Despite extensive research on the control of human limb efforts, the basic mechanism of control in multi-segment limb force generation. has not been addressed. A novel technique will be employed to described the preferred mechanism of force generation in the lower limb by kinematically constraining the limb so that the foot force direction is free to vary. Health humans have been shown to increase foot force through the addition of force control that may be preserved post-stroke. The following hypotheses will be tested: 1) Hemiparametric humans generate linear foot force paths as previously observed in healthy humans. 2) The flexor/crossed extensor reflex produces linear force paths as previously observed in healthy humans. 2) The flexor/extensor reflex produces linear force paths. This work will increase understanding of the role flex neural circuits play in voluntary efforts. This characterization of post-stroke motor control and a potential neural mechanism will enable future research to evaluate the hypothesis that the rich variety of natural limb efforts are constructed on this basic neural mechanism. With this theoretical understanding of foot force control, therapies can be developed that restore functional gait by working within the constraints of the modified control system.